1.7.0 Release Plan

[silkeh]

1. [x] Ensure all issues in the milestone have been completed (except this one).
2. [x] Ensure the release is set in Makefile.
3. [x] Tag the 1.7.0 release.
4. [x] Update package in unstable:
   1. [x] Update the solbuild package.yml with the 1.7.0 release locally.
   2. [x] Verify builds for android-tools, glew, giflib, zlib-ng, zsh.
   3. [x] Verify subcommands: build, chroot, delete-cache, index, init, update.
   4. [x] Publish: https://github.com/getsolus/packages/pull/3850
5. [x] Smoke test in unstable.
   1. [x] Re-generate unstable image (and only the unstable image -- the stable users aren't on this version yet at this point)
6. [x] Deploy on build server:
   1. [x] Bump and push nano
   2. [x] Verify that history generation works
   3. [x] Update build server documentation with relevant checklist and notes
   4. [x] Update to the latest unstable image using Pickle Cache Version 2 payloads in a Version 4 gdbm FilesDB.